The static Atomics
.wait()
method verifies that a given position in an Int32Array
still contains a given value and if so sleeps, awaiting a wakeup or a timeout. It returns a string which is either "ok
", "not-equal
", or "timed-out
".
Note: This operation only works with a shared Int32Array
and may not be allowed on the main thread.
Syntax
Atomics.wait(typedArray, index, value[, timeout])
Parameters
typedArray
- A shared
Int32Array
.
index
- The position in the
typedArray
to wait on.
value
- The expected value to test.
timeout
Optional
- Time to wait in milliseconds.
Infinity
, if no time is provided.
Return value
A String
which is either "ok
", "not-equal
", or "timed-out
".
Exceptions
Examples
Using wait()
Given a shared Int32Array
:
const sab = new SharedArrayBuffer(1024);
const int32 = new Int32Array(sab);
A reading thread is sleeping and waiting on location 0 which is expected to be 0. As long as that is true, it will not go on. However, once the writing thread has stored a new value, it will be notified by the writing thread and return the new value (123).
Atomics.wait(int32, 0, 0);
console.log(int32[0]); // 123
A writing thread stores a new value and notifies the waiting thread once it has written:
console.log(int32[0]); // 0;
Atomics.store(int32, 0, 123);
Atomics.notify(int32, 0, 1);
Specifications
Browser compatibility
| Desktop | Mobile | Server |
---|
| Chrome | Edge | Firefox | Internet Explorer | Opera | Safari | Android webview | Chrome for Android | Firefox for Android | Opera for Android | Safari on iOS | Samsung Internet | Node.js |
---|
wait | Chrome
Full support
68-
Full support
68
-
No support
60 — 63
- Notes Chrome disabled
SharedArrayBuffer on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This was a temporary removal while mitigations were put in place.
| Edge
Full support
79-
Full support
79
-
No support
16 — 17
- Notes Support was removed to mitigate speculative execution side-channel attacks (Windows blog).
| Firefox
Full support
78-
Full support
78
-
Full support
57
- Notes Support was disabled by default to mitigate speculative execution side-channel attacks (Mozilla Security Blog).
- Disabled From version 57: this feature is behind the
javascript.options.shared_memory preference (needs to be set to true ). To change preferences in Firefox, visit about:config. -
No support
55 — 57
-
No support
48 — 55
- Disabled From version 48 until version 55 (exclusive): this feature is behind the
javascript.options.shared_memory preference (needs to be set to true ). To change preferences in Firefox, visit about:config. -
No support
46 — 48
Notes Alternate Name Disabled - Notes The method returns values
Atomics.OK , Atomics.TIMEDOUT , and Atomics.NOTEQUAL , instead of the later-specified strings. - Alternate Name Uses the non-standard name:
futexWait - Disabled From version 46 until version 48 (exclusive): this feature is behind the
javascript.options.shared_memory preference (needs to be set to true ). To change preferences in Firefox, visit about:config.
| IE
No support
No | Opera
No support
No | Safari
No support
10.1 — 11.1 | WebView Android
No support
60 — 63-
No support
60 — 63
- Notes Chrome disabled
SharedArrayBuffer on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This is intended as a temporary measure until other mitigations are in place.
| Chrome Android
No support
60 — 63-
No support
60 — 63
- Notes Chrome disabled
SharedArrayBuffer on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This is intended as a temporary measure until other mitigations are in place.
| Firefox Android
Full support
57-
Full support
57
- Notes Support was disabled by default to mitigate speculative execution side-channel attacks (Mozilla Security Blog).
- Disabled From version 57: this feature is behind the
javascript.options.shared_memory preference (needs to be set to true ). To change preferences in Firefox, visit about:config. -
No support
55 — 57
-
No support
48 — 55
- Disabled From version 48 until version 55 (exclusive): this feature is behind the
javascript.options.shared_memory preference (needs to be set to true ). To change preferences in Firefox, visit about:config. -
No support
46 — 48
Notes Alternate Name Disabled - Notes The method returns values
Atomics.OK , Atomics.TIMEDOUT , and Atomics.NOTEQUAL , instead of the later-specified strings. - Alternate Name Uses the non-standard name:
futexWait - Disabled From version 46 until version 48 (exclusive): this feature is behind the
javascript.options.shared_memory preference (needs to be set to true ). To change preferences in Firefox, visit about:config.
| Opera Android
No support
No | Safari iOS
No support
10.3 — 11.3 | Samsung Internet Android
No support
No-
No support
No
- Notes Chrome disabled
SharedArrayBuffer on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This is intended as a temporary measure until other mitigations are in place.
| nodejs
Full support
8.10.0 |
---|
Legend
-
Full support
- Full support
-
No support
- No support
- See implementation notes.
- See implementation notes.
- User must explicitly enable this feature.
- User must explicitly enable this feature.
- Uses a non-standard name.
- Uses a non-standard name.
See also